Professional video tape recording and editing equipment contains various operator manipulated controls, both rotary and linear controls, as well as push-button controls. In video tape reproducing apparatus, certain functions or modes are initiated under operator manual control, such as shuttle, jog or variable play speed, where a single knob is used for multiple functions and each function requires that the knob have a different set of mechanical characteristics.
In the use of such rotational control devices, it is preferable that such devices have a "feel" representative of the type of control or operation being effected. In particular, upon manual rotation by an operator, through a given angular displacement, or to a present angular position, at a given rotational speed, or upon accelerated rotation, ideally through the use of the tactile sense, the operator should receive tactile feedback of the extent and limit of motion.
In one such device, shown and described in U.S. Pat. No. 4,560,983, entitled Dynamically Responsive Control Device and System, issued Dec. 24, 1985 to Williams and assigned to Ampex Corporation, the assignee of the present invention, a knob is coupled to a shaft, a tachometer and a particle brake, with a control system receiving information from the tachometer to control the operation of the particle brake to thereby provide tactile feedback to the operator.
Another such device is shown and described in U.S. Pat. No. 4,859,922, entitled System for Controlling the Operating Mode of a Controlled Apparatus, such patent issuing to Tauchenitz et al., on Aug. 22, 1989. The patent discloses an apparatus control system including an operating knob having a toroidal coil positioned concentrically with respect to the axis of rotation thereof with a brake magnetically coupled to the coil and mechanically coupled to the knob, the brake being effective up to a predetermined angular deflection. Direction of rotation, rotary or angular deflection from a zero or null position, and axial deflection or shift of the shaft, coupled to the knob, is sensed or scanned, and knob movement signals are derived which are coupled to an electronic processing system.
A traditional method for accomplishing the tactile feel in a video tape recording system is to use an optical encoder coupled with a magnetic particle brake, with the two assembled into a single unit. The output of the encoder is decoded into direction information, and the particle brake is used to provide the detent or feedback information to the operator through the knob. Such devices are very expensive, in component cost as well as assembly.
Such prior art devices require special construction that adds to the cost of such knobs. Furthermore, such devices tend to be complicated in operation as well as construction.
In accordance with the present invention, there is provided a new and improved rotary control device with tactile feedback, utilizing a stepper motor coupled for rotation by a control knob.